1. Field of the Invention
The present invention relates to a method for manufacturing a magnetoresistance head and, more particularly, a method for manufacturing a magnetoresistance head including a step of forming patterns by virtue of lift-off technique.
2. Description of the Prior Art
A magnetoresistance head utilized as a reproducing head of a magnetic recording apparatus has the configuration as shown in FIG.1, for instance. The magnetoresistance head is implemented by forming sequentially a SAL (Soft Adjacent Layer) 102, a nonmagnetic layer 103, and a magnetoresistance layer (referred to as xe2x80x9cMR layerxe2x80x9d hereinafter) 104 on a lower gap layer 101, then patterning these three layers as a planar rectangular pattern, and then forming antiferromagnetic layers 105a, 105b and lead terminals 106a, 106b on both sides of the rectangular pattern. A region formed between two lead terminals 106a, 106b serves as a sense region S.
A pair of lead terminals 106a, 106b are formed by lift-off process, as described below with reference to FIGS. 2A to 2C.
Referring to FIG. 2A, a resist 107 is coated on the rectangular pattern of the SAL 102 one time, the nonmagnetic layer 103, and the MR layer 104 and on the lower gap layer 101. The resist 107 is then patterned by exposing and developing the resist 107 so as to expose two lead terminal forming regions and to cover the sense region S on the MR layer 104. As shown in FIG. 2B, the antiferromagnetic layer 105 and the metal film 106 are formed by sputtering. In turn, the resist 107 is released to leave the metal layer 106 only on two lead terminal forming regions. The antiferromagnetic layer 105 and the metal film 106 are thus left only on two lead terminal forming regions, which are used respectively as the antiferromagnetic layers 105a, 105b and the lead terminals 106a, 106b, as shown in FIG. 2C.
However, in the event that side portions of the patterned resist are patterned to form vertical flat surfaces, there is caused such a drawback that flashes are apt to be generated on peripheries of the lead terminals 106a, 106b. 
In order to suppress such flashes of the lead terminals 106a, 106b, it has been known to use the resist having a two-layered structure.
For instance, as has been recited in U.S. Pat. No 5,087,332 and Patent Application Publication (KOKAI) 3-125,311, the resist is coated two times to prepare for patterning of the gap layer in the magnetic head, then sectional shapes of the resist are formed to have a mushroom-like sectional shape by exposing and developing the resist two times, then the resist is used as a lift-off mask. In addition, the lift-off mask having such mushroom-like sectional shape in which the upper layer and the lower layer consist respectively of the resist and the Al2O3 film has been recited in Patent Application Publication (KOKAI) 7-65,326.
However, if relative misalignment of mask positions occurs during exposure process since these masks are processed by two-time patterning, the mushroom-like sectional shapes may be unbalanced on the right and left sides, otherwise the resist may be curved because the upper resist layer has projected too much laterally. Hence it becomes difficult to improve manufacturing yield of the magnetic head.
Furthermore, there are some cases where the resist having the mushroom-like sectional shape is used commonly as the lift-off mask as well as the mask for forming the magnetic layer pattern. In this event, since the resist is damaged in the course of vacuum process, constituents of the resist such as the organic substance are scattered from the resist and stick to the surface of the magnetic layer. This causes defective contacts between the magnetic layer and the lead terminals.
In addition, if release liquid for the two-layered resist and other conditions are improper, the magnetic layer is also damaged.
An object of the present invention is to provide a method for manufacturing a magnetoresistance head by which the films can be patterned with good precision and damage of the resist can be suppressed.
According to an aspect of the present invention, edges of pattern of an organic film formed to cut inwardly from edges of pattern of a resist film by forming the organic film on a multilayered film constituting a magnetoresistance device, then forming the resist film on the organic film, and then patterning the organic film and the resist film. A cut-into amount is defined to such an extent that particles of an upper thin film such as a magnetic film or a metal film which is formed by sputtering or vacuum evaporation on the organic film and the resist film do not stick to side portions of pattern of the organic film.
Therefore, even if the pattern is formed by virtue of lift-off while employing the organic film and the resist film as the mask so as to leave the upper thin film only on the multilayered film, no flash is generated on the pattern of the upper thin film.
If inorganic film is utilized in place of the resist film, generation of the flash can be prevented. In case the mask is also employed in ordinary photolithography, contaminants made of mask constituting substances can be suppressed from sticking to the magnetoresistance device by reducing scattering of the mask because of etching if the upper layer of the mask is formed of the inorganic film. In addition, in case the inorganic film is formed of metal and terminals are formed by virtue of lift-off, contact resistance between the terminal and the magnetoresistance device is in no way increased since the contaminants which adhere to the surface of the magnetoresistance device are metal.
In the present invention, in the mask of a two-layered structure having a pattern to cover the sense region, since the width of the mask is widened around the sense region, the upper layer of the mask is kept in a floating state even when the lower layer of the mask in the sense region is lost in the course of manufacturing the mask. Therefore, no trouble is caused in lift-off.
In case the lift-off mask having a substantial T-like sectional shape is formed, compressive stress is generated in the upper layer. For this reason, since the upper layer is curved downwardly, contaminants scattered from the mask may stick to the magnetoresistance device. If compressive stress is set within less than 0 dyn/cm2 but more than xe2x88x9220.0xc3x97109 dyn/cm2, excessive curvature of the upper layer can be prevented.
Furthermore, if compressive stress in the upper layer of the mask is increased as its location in the upper layer becomes higher, curvature of the upper layer becomes small as the upper layer of the mask is etched even when the mask is employed in both patterning steps in photolithography and lift-off. Therefore, there is no trouble in succeeding with lift-off.
In the step where the lower film of the mask is formed of a photosensitive organic film and the upper film thereof is formed of the inorganic film, whole image exposure of the organic film may be effected prior to formation of the inorganic film. Thus, reduction in mask precision which is caused by degradation in photosensitivity because of heat generated in forming the inorganic film can be prevented.
According to another aspect of the present invention, since patterning is carried out after patterning of the magnetoresistance device is completed if the shielding film, etc. beneath the magnetoresistance device are patterned, the resist used when the magnetoresistance device is patterned is flattened, so that precise patterning of the magneto-resistance device can be implemented.
According to still another aspect of the present invention, since the multilayered film is patterned while employing the organic film and the resist film as another mask prior to patterning of the upper thin film by lift-off, time and labor for preparing the mask every patterning can be omitted and throughput can be improved. In this case, if the etching rate of the resist film on the organic film by virtue of argon sputter etching is less than 450 xc3x85/min under the predetermined conditions, both contamination of the surface of the multilayered film by the constituents of the organic film and contamination of the surface of the nonmagnetic layer beneath the multilayered film can be extremely reduced. Furthermore, since the crosslinked negative resist or the organic silicon resin has a small etching rate by virtue of sputter etching, they are fitted for the resist material. Similarly, since the chemically amplified resist formed of material including soluble resin, crosslinking agent, and acid generating photo-generating agent also has a small etching rate, it is preferable to use the chemically amplified resist as the resist film above mentioned.
As another method for reducing the etching rate of the resist film, there is a method for curing the resist film by means of heating or excessive light irradiation. The cured resist film has the advantage that generation of contaminants can be suppressed and reduction in dimension of the resist film per se can be suppressed in etching.
In the event that patterning of the organic film is effected continuously succeeding to patterning of the resist film by the liquid developer for the resist film, pattern precision of the organic film is enhanced if the velocity of dissolution ratio is set to more than 10. If the organic film is patterned by a dry process such as oxygen plasma and while employing as the mask the resist film including organic silicon as a major constituent, a planar profile of the organic film can be readily controlled by controlling the process time.
Resin having vinyl alcohol structure, resin including carboxylic acid group, or resin including sulfonic acid suitable substances for the organic film.
In case resin including polyamic acid is used as the organic film, the organic film may be baked at a temperature of 120 to 170xc2x0 C. for 1 to 20 minutes. Under remaining temperature and time, the etching rate at which the resin film is patterned is excessively fast or late, so that patterning of the organic film becomes difficult.
In the event that the photosensitive substance is employed as the lower organic film of the mask, precise latent images can be formed on the exposed organic film if the pattern of the upper resist film is used as the exposure mask for the organic film. Since irregular reflection of the light is caused in the region of the organic film which is not irradiated by the light, the light enters inwardly so that the not-exposed region of the organic film becomes narrower than the pattern of the resist film. By employing different sensitivity of photoreaction in the photosensitive organic film and the resist film, the pattern of the resist film can be formed larger than the pattern of the organic film by virtue of one-time exposure, to improve its throughput.
When the organic film is coated by spin-coating, the thickness of the organic film becomes uneven if the organic film is excessively thin. On the contrary, particles of the upper thin film formed on the resist film by sputtering readily sticks to side portions of the pattern of the organic film if the organic film is excessively thick, which causes the flash.
In order to coat the organic film and the resist film forming the mask in uniform thickness, smaller difference in the level existing beneath the mask is preferable. Therefore, after lift-off by removing the mask, it is desired to effect patterning of the nonmagnetic layer after patterning of the magnetoresistance device.
In order to prevent mixture of the organic film and the resist film, the intermediate layer may be located between them.
When the organic film is released from the resist film, the releasing rate is accelerated to improve its throughput if optimal removing liquids for respective the organic film and the resist film are used independently.